For some, this glitch has occurred after several hours of play, resulting in a substantial amount of lost progress.

According to Ubisoft's UK forum manager, the error has been reported to the Ubisoft team. He also suggests that anyone experiencing similar issues contact the support team over on this page to help them get to the root of the problem.

We have reached out to Ubisoft ourselves, and are awaiting a response.

In the meantime, if you're currently working through the Assassin's Creed III: Liberation, we recommend you save regularly, and, perhaps back up your progress using the content manager.